Switching device for electric circuits.



M. KALLMANN, DIEGD.

P. KAI-LEARN, ADMINISTRATRIX. SWITCHING DEVICE FOR ELECTRIC CIRCUITS.

APPLICATION FILED JUNE 26, 1906.

Patented Jan. 27, 1914.

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COLUMBIA ILANOCIRAPH CO.,WASHINUTON, D. c.

UNITED STATES T OFFICE.

MARTIN KALLMANN, OF BERLIN, GERMANY; PAULA KALLMANN, OF BERLIN, GERMANY,ADMINISTRATRIX OF SAID MAR-TIN KALLMANN, DECEASED.

SWITCHING DEVICE FOR ELECTRIC CIRCUITS.

Specification of Letters Patent.

Application filed June 26, 1906.

Patented Jan. 27, 1 914. Serial No. 323,538.

To all "Iii/L01 it may concern Be it known that I, Dr. MARTIN KALL-MANN, a subject of the Emperor of Germany, residing at new and usefulImprovements in Switching Devices for Electric Circuits; and I do herebydeclare the following to be a full, clear, and exact description of thelnvention, such as will enable others skilled in the art to which itappertains to make and use the;

same.

My invention relates to devices in cutouts, reversing-switches,automatic contactbreakers, cell-switches, and the like, and has for itsobject the prevention of violent breaksparks and flashing at thecontacts, though it can also be employed with advantage to preventextra-currents on the interruption of circuits with high self induction.This is attained by inserting in the circuit at the contact point orplace of break or reversal a resistance of high temperature coefficient,especially iron, which on passage of current increases, on being heatedto red-heat, many times in resistance and thus weakens the currenttosuch an extent that the final interruption of the circuit takes placealmost without sparking and, any extra-currents remain but small.

Figures 1 and 2 show the changes in cur- I l l Kurfiirstendaunn 4-0/4],5 Berlin, Germany, have invented certam l l l l I rent strength in a.circuit during the oper i ation of cuttlng off the current through a 1self-acting resistance as in my improved switch. Fig. 3 shows a singlepole switch and the connections between the supplementary switch and theself-actlng resistances.

Fig. I shows a bipol.ar switch with the acconnnlnymg resistance andsupplementary switch. Fig. shows means for controlling t thesupplementary switch by means of which the current is short circuitedthrough the re- 5 sistance. Fig. 6, shows a device in which an excess ofcurrent causes the breaking of the main circuit and the opening of abypath through the special form of resistance which I I provide. Fig. 7shows another device for accomplishing the same result. Fig. 8 shows theswitch as applied to an accumulator.

The resistance, in order to insure as small 5 a capacity for heat aspossible, may be made of very thin iron wire which for the purpose oipreventing oxidation may, like incandescent lamp filaments, be inclosedin a.

vacuum, for instance a glass box or better in an atmosphere of hydrogenor other indifi'ercnt gas. If for example, the resistance is calculatedfor a currentof 2 amperes. the voltage at its ends increases rapidlywith this current strength by reason of the heatmg, while the currentremains almost constant, provided that the iron resistance forms themain portion oil the circuit resistance. for example if the increase isfrom 10 to :30 volts. It is only when a higher ten'lperature is reachedthat the essential increase in resistance ceases and thecurrent-strength then increases further. In an iron wire for instance,036 nnn. thick there is 2 volts fall of potential for ampere current,that is 4 ohms resistance; for 1 ampere and mode-rate heating.correspondingly 5 volts and 5 ohms: tor 2 amperes and dark red heat,correspond ingly 22 volts and 11 ohms; for amperes and medium red heat50 volts and ohms: For 2.3 amperes and bright red heat 75 volts andabout 33 ohms. Thus if in a circuit of 220 volts there is a load of 20amperes corresponding to 11 ohms resistance of the lamps or the like,and it this load were cut out direct, there would be very considerablesparking caused. lt' however, there is introduced at the place of break,in suitable manner, a. reducing resistance, which in working isshort-circuited, then on, opening the switch the current at the firstmoment, (if this resistance when cold is about 4 ohms.) will be 22m....1amperes.

The break spark with this small change oi current (from 20 to 14.7) isnaturally but trifling. Vithin a few seconds the thin iron wire will nowbecome incandescent and increase in resistance to for instance, 33 ohms.The current-strength of the circuit then sinks to 220 r m a amperes.

and these remaining 5 amperes can likewise be interrupted without anyconsiderable sparking. The case is similar on direct short circuitingtaking place, where for instance, som Ir} amperes current only havestill to be interrupted. This process can be used without dilliculty bysimple bridging of the place of break either by a single or multiplepoleswitch, two breaks or it necessary more stages, being thus employed. Inthe latter case there are several sections of the reducing resistance tobe cut out in stages.

Any form of switch, such as lever, rotary l ture, so that the entirecircuit is broken.

or reversing switches with several contacts may be used. lf extremelythin iron wires of say l/ lO mm. thickness be used the redu ingresistance will under certain circumstances be heated to red heat inless than a second, so that a switch may be employed in which the mainand shunt circuits are opened in rapid succession.

The use of the reducing resistance is particularly important forautomatically opening the circuit. This automatic operation may beapplied either only for the shunt switch, while the main switch isopened by hand, or the entire switching operation may be effected whollyautomatically. In the first case, as long as the main switch is closed(preferably positively), the shunt switch is also closed, and thereduciru resistance thus short circuited. As soon as the main switch isopened the reducing resistance is cut into the place of break and theworking current will flow through it. The current now falls again, asalready explained, within a few seconds, by reason of the heating of thereducing resistance, and when it has reached a suitably small value, forexample in the above case 5 amperes, an electromagnet, which istraversed either wholly or partly by the main current, releases itsarmature, which now interrupts the remaining current by cutting out theshunt (reducing resistance).' Thus the electromagnet armature falls ofitself shortly after opening of the main switch. This can naturally alsobe done gradually in several stages if necessary by means of severalelectromagnets or electromagnetic armatures. For the circuit however,the danger of too great currentstrength is removed immediately onopening of the main switch, since the rapidly increasing reducingresistance the intensity. lVith entirely automatic switching the matteris similar. The reduc ing resistance is combined with an automaticdevice of suitable construction. 'Whcn the current is excessive the maincontact is opened by the operation of a solenoid and the iron resistanceis interposed in the path of the current, causing the latter to fall,and. the circuit is then fully opened by the operation of thesupplementary switch. The lirst electromagnet would thus soon effect thefirst interruption in well known manner on too strong a current passing,while tie second electromagnet would release its armature on asufficiently weak current flowing, thus operating similarly to a Zeroautomatic switch or a minimum-current cut-out. the maximum and minimumswitching may be done simply by single electromagnet which first withtoo strong a current attracts an armature, thus cutting in the reducingquickly diminishes resistance, and then when the current issullicienl'ly weakened again, releases the armaln this case suitabledouble lever switches and the like are necessary for the contacts (amain and a secondary contact).

The combination of the electro-magnet with one or more armatures may bevaried as desired corresponding to the construction of the automaticdevice, the modern electroniagncts of pot or other shape, boxed in asfar as possible, being preferably employed.

ln the same manner distance switches, rerersing-switches, double poleswitching devices, etc., with the aid of reducers enable practicallysparkless break. Similarly circuits with high self-induction (forinstance magnetic fields of dynamos or motors) can be broken in thismanner without strong extra currents being caused. The action of thereducer when applied to cell-switches ol': accumulators is similar. Herethe iron wire reducer is inserted in. well known manner between thetwo-part cell-switch crank, 0]; Elle. sliding contact, instead of theusual constant resistance. As soon as tle contact bridges a cell, astrong current will llow through the iron resistance and the value ofthe latter will rapidly increase, so that the discharging current of thecell is quickly den'eased. The advantage here attained is that both theinitial spark on closing the cell on the initially very small (cold)resistance. and the subsequent spark on cessation of closin by reason ofthe then very weak discharging current (since the resistance is inhighly incandescent state) are but very small, smaller than when forinstance nickeline-resistance, as usually employed for bridging in cellswitch contacts, is used. This is of special importance when two cellshave to be connected to each contact, for instance with 440 voltinstallations.

One form of device for carrying out the ab ve described invention isillustrated diagrammatically in 3.

When opening the switch 1 the secondarv switch 2 is still closed, sothat the whole current to be consumed, which undergoes a.proportionately small weakening in conse quence of the still coldreductionsresistancc 3. flows through the lamps 4, or the like, and thesaid reduction-rcsistance. After a few seconds, the resistance 3 hasbecome red-hot. and has consequently been greatly increased. llow theswitch 2 can be opened without much sparking, as the current has in themeantime been reduced autou'iatically to a sm: ll fraction of itsinitial value. Serious sparking is thus avoided, on opening the mainswitch and also on opening the supplementary switch. On closing thecircuit. the switcn 2, or the switch 1, may at will be closed first, orboth may be closed at the same time. On opening them, the secondaryswitch of the reduction-resistance must always follow the main switch,for this secondary switch causes the interruption of the rest of thecurrent.

Fig. 4 represents the system applied to a bipolar switch. Only onereduction-resistance is needed, but it is better to use two r sistances,shown at 3, which are connected both to a branch lead, and the twoswitches are then made bipolar in the usual way for reducing thebreak-spark. The working will, at once be seen from the precedingdescription. The circuit containing an inductive load 5 is in the firstplace broken by means of the switch 1 and then finally by the switch 2.If very thin iron spirals of an exceedingly small heating capacity areused, the reduction-resistance, which is considerably overloaded by highcurrents to be broken, or extra currents, becomes red-hot in some casesin less than one second, so that a single quick break switch may be usedinstead of two switches.

The opehing of the secondary circuit can also be effected automaticallyin a very simple manner, especially by using reductionresistances whichdo not become incandescent instantaneously, but only after a fewseconds, as illustrated in Fig. 5. Here the current flows from thepositive pole in the first place through a coil of a small electromagnet11, passes over the pivot 12 into the knife of the lever-switch 1, andwould, if the circuit were closed, flow in the direction of the arrowover contact 14 into the outer circuit, and from here to the negativepole. If resistance is intercalated, the electromagnet- 11 is excitedand attracts its armature 15, against the action of the spring 17, sothat the secondary contact 19, 20, and through the same reductionresistance 3 are likewise connected, but in consequence of theshort-circuiting by the main lever only a weak current fiows throughthem. During the switching off of the lamps or motors, the armature 15would keep the contact 19, 2O closed for an adjusting screw 21 of themain lever insures the mechanical closing of the secondary contact, aslong as the main lever is closed. If the main lever switch 1 is openedand the contact broken at 14, the whole current then flows over thearmature 15 of the electroi agnet through 19 and 20, and thereduction-resistance 3, and from here over the outer circuit to theminus pole. The breakspark at the main contact 14 is only small onaccount of the by-path over the reduction-resistance, which offers onlya small resistance. After the interruption at 14, the armature 15 of theelectromagnet is still held attracted by the electron'zagnet 11, as astrong current still flows through the windings 10. During the increasedheating of the reduction-resistance this current sinks,

r l l l l 1 I however, within a few seconds to a fraction of the initialvalue, for instance, as shown by figures at the beginning, from about 15to 5 amperes. Armature 15 is released by a spring 17, the contact 19, 20is broken, and the circuit therefore fully opened. The secondary contactthus ii'ollows automatically the main contact, according to the load onthe circuit, for if the strength of the current is very small, thearmature 15, after the opening oi the main lever, drops at once otl' theelectromagnet. The greater the load is the longer it takes until thecurrent has been weakened suiiiciently, whereupon the secondary circuitis likewise broken. By closing the main switch 1, that is to say, byconnecting the load, the contact 19, 20 is mechanically andautomatically closed by means of the adjustable screw 21, so that thesecondary circuit is always ready to prevent the break-spark as long asthe main switch is closed. This form may in the same manner also beadapted for bipolar switches.

Fig. 6 shows in a diagrammatic view the same system for a selfactingswitch, which. on a certain strength of current being reached, isintended to break a circuit, while Fig. 7 shows a practical form ofconstruction of a self-acting switch. In Fig. 6 the main contact 23, 24is closed by a hooked lever 26, pivoted at 27. Contact 23 is connectedwith a spring 28. The path of the current over the reduction resistance3 is broken by the contact and 31. If the current in the releasingelectromagnet reaches a certain strength it attracts the armature 33,the lever 26 releases the contact 23 (pivoted at 34) from 24, the maincontact is opened, and the current flows at the other end of thetwo-armed lever, which at 35 contains an insulating-piece (the secondaryCO11- tact 30, 31 being closed) and through the reduction-resistance 3,into the outer circuit. Here the current is only slightly reduced. asthe resistance is still cold. In a very short time, however, forinstance after 1 to 2 seconds, the resistance becomes red-hot and inconsequence the resistance of the circuit consisting of the lamps orother loads and the reduction-resistance, rises so high that thestrength of the current in the electromagnct sinks very considerably,for instance down to about the eighth part. In consequence of this thearmature 33 drops oil from the electromagnet under the influence of thespring 30. and thereby the whole circuit, inclusive of therechlotion-resistance, is opened.

W hile in Fig. 6 the operation of the main lever is effected directly byan ordinary electromagnet, the effect is produced. in Fig. 7 in adifferent way, which allows of in creasing the sensibility of theelectromagnet. Here a special form of the electromagnct shunted to aresistance 3, which may either be formed after the usual manner of themain current resistances or of a resistance of a high temperaturecoetficient (for instance, iron) for increasing its sensibility. Thecurrent therefore flows, if the main switch 1 is closed, through thisinto the resistance 3 of the main circuit, and through the coil of theelectromagnet a0, branching off from the same, into the outer circuit.it the current rises above a certain intensity, the iron core 41 isdrawn into the coil of the electromagnet and releases the pawl 42 fromthe hook as, whereby the main switch 1 standing under the action of thespring at and pivoted to L5 is released from the contact 4L6. Hereby thesecondary contacts 47, t8 are also released by the adjusting screw 4:9but remain still in contact, in consequence of being stopped by pawl 42and hook 43. This keeps the secondary circuit closed through thereduction-resistance 3. Only when the intensity of the current, inconsequence of the increased heating of 3, has sunk considerably, theiron core 4-.1 drops down into the coil of the magnet t0 (the switchbeing mounted vertically) and strikes against pawl 42, which newreleases the hook 13 of the lever 51, so that the latter under theinfluence ot the spring 52, opens th secondary contact and completelybreaks the circuit. According to the preceding calcu lations andexamples, the opening of the main contact, as well as of the secondarycontact, takes place without much sparking. In the same manner,distance-switches, reversing-switches, double pole switching devices,etc., with the aid of reducers, produce a practically sparkless break.Similarly circuits with high self-induction (for instance magneticfields of dynamos or motors) can be broken in this in anncr withoutstrong extra currents being caused. The action of the reducer whenapplied to cell-switches ol accumulators is similar, as shown in Fig. 8.This is of special importance when, for example, two cells have to beconnected to each contact, for instance with &0 volt installations. Hereis intercalated instead of the usual constant re stance, which consists.as a rule, of some windings of nickeline wire, or the like, areduction-resistance 3 of iron, or the like, inclosed it necessary in aglass reservoir with hydrogen, between the crank ot the cell-switchformed of two parts 60 and 61. The secondary contact 61 is insulated inthe usual manner fr m the main contact and from the axle (32. or thecurrent supply, by an insulated piece (55. In the position shown in thedrawing, the currentwould on moving the eell-switch flow from contact6?) over 60, 3, 61, (34L. As the resistance 3 was thus far still cold,there does not take place during this movement of the crank oi": thecell-switch any noticeable weakening of the outer circuit, and theretoreno reduction of the tension. Now the reduction-resistance 3 is heateduntil it becomes red-hot, and its ohmic value is thereby considerablyincreased and the rate of discharge of the cell or cells of theaccumulator is thereby lessened. ll ithin one second the cell-switch maynow be moved one cell farther on, in consequence of which theshort-circuiting of the cell. by the reduction resistance ceases,without the formation of any considerable break-spark, for the currentto be broken is then only very weak. T he same operation is repeated andthe spark is very small on the succeeding contacts, in consequence ofthe described properties of the reduction-resistance, which during itsmovement from cell to cell must have suiticient time to alternately cooldown and get hot. In this way all other devices for the arresting ofsparks can be entirely dispensed with, while violent shocks of currentduring the movement of the cell-switches and reactions upon the tensionof the system are reduced to a minimum, in consequence (it the describedproperties.

Having thus described my invention. what 1 claim as new is: i

l. The combination of: an electric circuit. a switch therein, a secondcircuit, a supplementary switch and a resistance of a high positivetemperature coetticient in the second circuit and means whereby thelatter switch is operated by the operation of the main switch in onedirection, said supple nientary switch being mechanically indc' pendentof the operation of the main switch in the other direction, meansoperated by an excess of current for opening the main switch, and amember also operated by such means for releasing the supplen'ientarvswitch. I

The combination of an electric circuit, a switch therein, a secondcircuit, a supplementary switch therein, the latter being me chanicallyindependent of the operation oil the main switch during the openingoperation. and electrical and mechanical means autmnatically operatedtor opening the supplementary switch at an interval after open ing themain switch, such electrical means including a conductor having a highpositive temperature coetlicient connected with the supplementaryswitch, the duration oi said interval. being determined, by the effectof the current on such conductor.

3. In. an electric switch the combination et a main switch, asupplementary switch 'acent thereto, mechanical means for closthesupplementary switch by the operaon of the main switch, and electricaland mechanical means ii or automatically opening the supplementaryswitch at an interval utter the opening ot the main switch, suchelectrical means including a conductor having a high positivetemperature co-eflicient connected with the supplementary switch, theduration of said interval being determined by the effect of the currenton such conductor.

4-. In an electric switch the combination of a main switch, asupplementary switch adjacent thereto, adjustable mechanical means forclosing the supplementary switch by the operation of the main switch,and electrical and mechanical means for auto matieally opening thesupplementary switch at an interval after the opening of the mainswitch, such electrical means including conductor having a high positivetemperatune eo-eflicient connected with the supplementary switch, theduration of said interval being determined by the effect of the currenton such conductor.

The combination of a main electric cir" cuit, a switch therein, a secondcircuit, a supplementary switch therein, a device on said main switchadapted to contact with said supplementary switch, a resistance of ahigh positive temperature coefficient in the second circuit, a solenoid,a pawl actuated by the armature thereof for releasing the main switch,and means engaging the supple inentary switch and holding it closeduntil the current passing through the solenoid is sufliciently reducedto cause the armature to return to its normal position.

6. The combination of a main electric cireuit, a switch therein, asecond circuit, a supplementary switch therein, hooks on each of saidswitches, a solenoid, a pawl engaged by the armature thereof when anexcess of ciurrent is caused to pass through said solenoid, said pawlwhen operated releasing and openin the main switch, a second pawlsimultaneously engaging the hook on the suppleineutary switch andholding it closed while the excess of current is passing through thesolenoid, means connected with the main switch adapted to contact withthe supplementary switch and a resistance of a high positive temperaturecoefficient in said second circuit.

7. The combination of an electric circuit, a switch therein, a secondcircuit, supplementary switch therein, and a resistancehaving a, highpositive temperature coefficient in the second circuit, the latterswitch remaining closed after opening the main switch. and means foreffecting in connection with the resistance the automatic release of thesupplementary switch after an interval following the opening of the mainswitch.

In testimony whereof, I afliX my signature, in presence of twowitnesses.

Du. MARTIN KALLMANN. lVitnesses lVoLDnrmR IIAUPT, HENRY HAsPER.

Copies 01' this patent may be obtained for five cents each, byaddressing the Commissioner of Patents,

Washington, D. C.

